Labeling apparatuses are used for applying labels with product information, advertising communications etc. to packages and goods. The labels used for this purpose are mostly self-adhesive labels which adhere, for example, to a backing strip and are wound together with this on a label dispensing roller of a label dispensing device. The label is separated from the backing strip as a result of a strong deflection about a removal bar and dispensed to the label receiving surface of a so-called air-blast labeling device. The label is first of all drawn in by means of underpressure and subsequently blown automatically onto a package or article conveyed passed it with a blast of compressed air.
The labels of the various types of goods are very different in their size and shape depending on the information content and advertising design.
It is known from U.S. Pat. No. 2,787,104 to adapt a suction head for holding a label in a labeling machine to the length of the label in that a slide element in the form of a plug is inserted to varying depths into a suction chamber so that the suction bores not required are covered.
Known labeling apparatuses operate with air-blast labeling devices, in which a label suction or receiving plate provided with holes or slots is used at the same time for drawing in and blowing the label onto the article. A continuous underpressure is generated in the air-blast labeling housing and this is switched over to compressed air for a short time via a valve, for blowing the label onto the package. The blast of air through the holes or slots of the receiving plate which is thereby generated causes the label to fly away in the direction of the package. This simple embodiment does, however, have the disadvantage that during the processing of labels which are smaller than the receiving plate the degree of efficiency of the blow-on function onto the package deteriorates. The openings not covered by the label lead to a loss in pressure energy during the switchover to the pulse of compressed air. This means that the blow-on energy and thus the quality of adhesion on the package is reduced. Moreover, the flight path of the label is influenced negatively by the air jets of the openings located outside the label surface.
DE 24 12 691 discloses an embodiment which eliminates the above disadvantages by having separate underpressure and pressure chambers present in the air-blast labeling housing.
An additional air-blast apertured plate is arranged above the suction plate at a distance therefrom and a pressure chamber is located above the apertured plate. For adaptation to the size and shape of the labels the air-blast openings in the air-blast apertured plate can be closed with screws or alternatively provided with long screw-in nozzles which bridge the space between air-blast apertured plate and suction plate and act on the label surface during the switchover to compressed air.
Air-blast openings can be covered or left open with an apertured mask usable above the air-blast apertured plate depending on the aperture pattern. The changeover to other label sizes is, however, complicated and time-consuming with this construction because a change of the apertured mask is necessary in this respect and a separate apertured mask must be kept ready for each label shape.